diff --git a/pkg/analyzer/test/generated/parser_fasta_test.dart b/pkg/analyzer/test/generated/parser_fasta_test.dart
index 85e78e01874..3f172299d6a 100644
--- a/pkg/analyzer/test/generated/parser_fasta_test.dart
+++ b/pkg/analyzer/test/generated/parser_fasta_test.dart
@@ -1062,6 +1062,17 @@ main() { // missing async
         ]);
   }
 
+  void test_constructor_this_cascade_synthetic() {
+    // https://github.com/dart-lang/sdk/issues/37110
+    parseCompilationUnit('class B extends A { B(): this.. {} }', errors: [
+      expectedError(ParserErrorCode.MISSING_ASSIGNMENT_IN_INITIALIZER, 25, 4),
+      expectedError(ParserErrorCode.EXPECTED_TOKEN, 29, 2),
+      expectedError(ParserErrorCode.MISSING_IDENTIFIER, 32, 1),
+      expectedError(ParserErrorCode.MISSING_FUNCTION_BODY, 33, 1),
+      expectedError(ParserErrorCode.EXPECTED_EXECUTABLE, 35, 1),
+    ]);
+  }
+
   void test_constructor_this_field() {
     // https://github.com/dart-lang/sdk/issues/36262
     // https://github.com/dart-lang/sdk/issues/31198
diff --git a/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart b/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
index 3a37ce61958..f85a2d35a43 100644
--- a/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
@@ -26,7 +26,8 @@ import 'error_token.dart'
 
 import 'keyword_state.dart' show KeywordState;
 
-import 'token.dart' show CommentToken, DartDocToken, LanguageVersionToken;
+import 'token.dart'
+    show CommentToken, DartDocToken, LanguageVersionToken, SyntheticStringToken;
 
 import 'token_constants.dart';
 
@@ -247,6 +248,9 @@ abstract class AbstractScanner implements Scanner {
   /// Append [token] to the token stream.
   void appendErrorToken(ErrorToken token);
 
+  /// Prepend [token] to the token stream.
+  void prependErrorToken(ErrorToken token);
+
   /**
    * Returns a new comment from the scan offset [start] to the current
    * [scanOffset] plus the [extraOffset]. For example, if the current
@@ -790,7 +794,11 @@ abstract class AbstractScanner implements Scanner {
         hasDigits = true;
       } else {
         if (!hasDigits) {
-          unterminated(messageExpectedHexDigit, shouldAdvance: false);
+          prependErrorToken(new UnterminatedToken(
+              messageExpectedHexDigit, start, stringOffset));
+          // Recovery
+          // TODO(danrubel): append actual characters not "0"
+          appendToken(SyntheticStringToken(TokenType.INT, "0", tokenStart));
           return next;
         }
         appendSubstringToken(TokenType.HEXADECIMAL, start, true);
diff --git a/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart b/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
index ffc82028f98..3ba37128fd4 100644
--- a/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
@@ -260,6 +260,7 @@ abstract class ArrayBasedScanner extends AbstractScanner {
     appendToken(token);
   }
 
+  @override
   void prependErrorToken(ErrorToken token) {
     hasErrors = true;
     if (_errorTail == tail) {
diff --git a/pkg/front_end/lib/src/fasta/scanner/recover.dart b/pkg/front_end/lib/src/fasta/scanner/recover.dart
index a54c94a9644..2998eccc526 100644
--- a/pkg/front_end/lib/src/fasta/scanner/recover.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/recover.dart
@@ -135,8 +135,7 @@ Token scannerRecovery(List<int> bytes, Token tokens, List<int> lineStarts) {
   }
 
   recoverHexDigit() {
-    return synthesizeToken(errorTail.charOffset, "0", TokenType.INT)
-      ..setNext(errorTail.next);
+    throw "Internal error: Hex digit error token should have been prepended";
   }
 
   recoverStringInterpolation() {
@@ -156,7 +155,9 @@ Token scannerRecovery(List<int> bytes, Token tokens, List<int> lineStarts) {
 
   // All unmatched error tokens should have been prepended
   Token current = tokens;
-  while (current is ErrorToken && current.errorCode == codeUnmatchedToken) {
+  while (current is ErrorToken &&
+      (current.errorCode == codeUnmatchedToken ||
+          current.errorCode == codeExpectedHexDigit)) {
     if (errorTail == null) {
       error = current;
     }
diff --git a/pkg/front_end/test/scanner_test.dart b/pkg/front_end/test/scanner_test.dart
index 932d67a0906..39a24acf5f4 100644
--- a/pkg/front_end/test/scanner_test.dart
+++ b/pkg/front_end/test/scanner_test.dart
@@ -303,7 +303,7 @@ abstract class ScannerTestBase {
   }
 
   void test_hexadecimal_missingDigit() {
-    _assertError(ScannerErrorCode.MISSING_HEX_DIGIT, 1, "0x");
+    _assertError(ScannerErrorCode.MISSING_HEX_DIGIT, 5, "a = 0x");
   }
 
   void test_identifier() {